Ask HN: healthcare.gov architecture

Reports are that the healthcare.gov site cost over $600m to rollout. Does anyone know specific details about the architecture of the site? Front-end, back-end, etc?

A quick look shows that healthcare.gov uses a couple of ASPs that we all should be familiar with - Chartbeat and Optimizely.

I'm really interested to see which technologies were chosen when a team has $600m to spend...